The disclosed technology relates to polyacetylene and chlorinated polyacetylene (CPA). More particularly, the disclosed technology relates to a process for polymerizing acetylene to produce polyacetylene and the so-produced polyacetylene, as well as a further process to obtain CPA from the so-produced polyacetylene and the CPA product.
Polyacetylene is generally not prepared by polymerizing acetylene in the gas phase. Acetylene in pure form is an unstable highly flammable gas that uncontrollably oligomerizes at high concentrations. Samples of concentrated or pure acetylene can easily react in an addition-type reaction to form a number of products, typically benzene and/or vinyl acetylene. This reaction is exothermic. Consequently, acetylene can explode with extreme violence if the pressure of the gas exceeds about 200 kPa (29 psi). Thus, acetylene is usually handled as a solution. Solution polymerization of acetylene is impractical on an industrial scale.
Gas phase polymerization is an industrial polymerization method used with gaseous monomers such as ethylene, tetrafluoroethylene and vinyl chloride. In this process, the monomer is introduced under pressure of, for example, about 1.38 Mpa (200 psi) into a reaction vessel containing a polymerization initiator. The process may be performed as a heterogeneous or homogenous process. In a heterogeneous process, the polymerization initiator is a solid whereas in a homogeneous process the initiator is a gas. Once polymerization begins, monomer molecules diffuse to the polymer chains growing on the polymerization initiator. In the heterogeneous process, the resulting polymer is obtained as a granular solid. Heterogeneous gas phase polymerization presents technical challenges with regard to acetylene due to acetylene's unstable nature.
One reference, Akagi, K., Suezaki, M., and Shirakawa, H., Synthesis of Polyacetylene Films with High Density and High Mechanical Strength, Syn. Metals, 28 (1989) D1-D10, teaches a non-solvent method for preparing polyacetylene films. The method employs low temperatures and does not employ a supported catalyst or produce a bulk powder.
Similarly, Forte, L., Lien, M. H., Hopkison, A. C., and Bohme, D. K., Carbocationic polymerization in the gas phase polymerization of acetylene induced by BF2+, Can. J. Chem., 68 (1990) 1629-1635, teaches a method for homogeneous gas phase polymerization of acetylene. The method employs ambient temperatures but does not employ a supported catalyst, produce a bulk powder, or produce true polyacetylene, i.e., a linear or substantially linear polymer consisting of repeat units equivalent to acetylene.
Another reference, Cataldo, F., Acetylene Polymerization on Rh(I) Complexes, Polymer, 1992, v. 33, No. 14, p. 3073-3075, teaches a solvent method to produce what is speculated to be linear polyacetylene films. The films produced are not characterized.
Due to the highly reactive nature of polyacetylene, most methods of characterization cause polyacetylene to react and change form. Thus, polyacetylene cannot be easily characterized. However, poly(di-functionalized acetylene) is very similar to polyacetylene. Because the difference between poly(di-functionalized acetylene) and polyacetylene is only two functional groups X, as shown below;
properties, such as molecular weight and atomic structure can be easily deduced from the functionalized version.
One example of a poly(di-functionalized acetylene) employed for testing purposes can be poly(di-chlorinated acetylene). Poly(di-chlorinated acetylene) can be easily tested, for example, by GPC, 13C-NMR, FTIR, TGA, DSC and SEM analysis. Moreover, a symmetrically chlorinated polyacetylene could provide benefits over current chlorinated polymers, such as CPVC.
Chlorinated Poly(Vinyl Chloride) (CPVC) has many useful properties. It is environmentally friendly, corrosion, chemical, and flame resistant, easily processable and cost effectively producible.
Current CPVC production is performed by a slurry process in water. In this process, PVC water slurry is treated with chlorine in the presence of UV light to form CPVC as shown in Graphic 1, and the resulting CPVC goes further into a compounding process to make the final product.

Despite the benefits of CPVC, the conventional slurry technique has many fundamental limitations, such as HCl generation after chlorination, compositional heterogeneity of the end product resulting in several different types of chlorinated segment units in the polymer backbone, a broad glass transition temperature range, a narrow processing temperature window, and strong dependence of raw material cost on volatile PVC price.
Poly(1,2-dichloroethylene) is a theorized but as yet unknown di-chlorinated polymer product in the CPVC family, differing from CPVC in its stereo-regularity as shown in Graphic 2. The polymer has long been thought of as the most attractive material within the CPVC family due to its theoretically excellent thermal properties. Poly[1,2-dichloroethylene] has been theorized to have a glass transition temperature (Tg) of about 270° C., much higher than the 155° C. average Tg for CPVC produced today. Poly[1,2-dichloroethylene] is also theorized to have a much higher softening point.

After over 30 years of pursuit, poly[1,2-dichloroethylene] has not been attainable by direct polymerization of 1,2-dichloroethylene monomers. Because polyacetylene is an insoluble polymer, researchers have reported on the chlorination of polyacetylene to impart solubility to the polyacetylene for purposes of characterization. However, chlorination of polyacetylene to produce poly[1,2-dichloroethylene] has never been reported.
U.S. Pat. No. 3,367,925 (issued Feb. 6, 1968 to Liu) teaches a method of polymerizing dichloroethylene. The product is called a symmetrical dichloroethylene polymer. However, the examples have not proven to be reproducible. Moreover, the product disclosed is not characterized in any manner, including by molecular weight or chlorine content.
Using a density-functional method, Springborg, Michael, Structural and Electronic Properties of Fluorinated and Chlorinated Polyacetylene, J. Am. Chem. Soc., 1999, 121 (48), pp. 11211-11216, calculated the electronic and structural properties of several polymers, including a (CCl)x structure, which represents poly[1,2-dichloroethylene]. The computations were theoretical to determine structure and bonding, no samples were actually made.
Cataldo, Frank, A Study of Chlorinated Polyacetylene, Eur. Poly. J., 1993, 29(12), pp. 1635-1639, chlorinated polyacetylene to obtain a polymer of poly[1,2-dichloroethylene]having disyndiotactic and atactic portions interspersed randomly by short polyacetylene segments, wherein the chlorinated polymer had a maximum chlorine content of 64 wt. % and a maximum decomposition rate at 170° C. Molecular weight was not reported.
Akagi, K., Kadokura, T., and Shirakawa, H., Stereospecific Chlorination of Polyacetylene by Chemical Doping, Polymer, 1992, 33(19), pp. 4058-4065 also teaches a chlorinated polyacetylene compound. However, neither the final chlorine content nor molecular weight is taught.
Matnishyan, H. A., Akhnazaryan, T. L., Voskanyan, P. S., and Korshak, Yu. V., Preparation of Soluble Functional Polymers by Modification of Nano-sized Polyacetylene, Eur. Poly. J., 2009, 45, pp. 1038-1045, teaches chlorinated polyacetylene having molecular weights up to 123,000. However, the polymers were only chlorinated up to 72 mol % calculated on the number of CHCl units in relation to the number of carbon atoms in the polymer backbone. Moreover, this reference teaches that solvent-based chlorination of polyacetylene produced by conventional slurry-phase acetylene polymerization gives a chlorinated product with significant levels of CH2 units (5-12 mole % by 1H NMR and 0.4%-10.4% by FTIR).
Not only is an easier and more industrially ready process needed to produce polyacetylene, but a polyacetylene compound is needed that can allow the production of a high molecular weight, highly chlorinated, symmetrical polyacetylene approaching true poly(1,2-dichloroethylene).